Structures of Mammeasins P and Q, Coumarin-Related Polysubstituted Benzofurans, from the Thai Medicinal Plant Mammea siamensis (Miq.) T. Anders.: Anti-Proliferative Activity of Coumarin Constituents against Human Prostate Carcinoma Cell Line LNCaP.

A methanol extract of the flowers of Mammea siamensis (Miq.) T. Anders. (Calophyllaceae) showed anti-proliferative activity against human prostate carcinoma LNCaP cells (IC 50 = 2.0 µg/mL). Two new coumarin-related polysubstituted benzofurans, mammeasins P ( 1 ) and Q ( 2 ), and a known polysubstituted coumarin mammea B/AC cyclo F ( 39 ) were isolated from the extract along with 44 previously reported polysubstituted coumarin constituents ( 3 - 38 and 40 - 47 ). The structures of two new compounds ( 1 and 2 ) were determined based on their spectroscopic properties derived from the physicochemical evidence including NMR and MS analyses and taking the plausible generative pathway into account. Among the coumarin constituents, mammeasins A ( 3 , IC 50 = 1.2 µM) and B ( 4 , 0.63 µM), sugangin B ( 18 , 1.5 µM), kayeassamins E ( 24 , 3.0 µM) and G ( 26 , 3.5 µM), and mammeas E/BA ( 40 , 0.88 µM), E/BB ( 41 , 0.52 µM), and E/BC ( 42 , 0.12 µM) showed relatively potent anti-proliferative activity.